1. Field of the Invention
The present invention relates to a fault detector for operating process of an electric arc furnace and a method thereof, which belongs to the technical field of fault detection.
2. The Prior Arts
Electric arc furnace operates by three-phrase AC power, and is used to melt ore and metal with the electric arc between the electrodes and the molten materials. In the operating process, the electric arc furnace produces lots of waste gas which is exhausted by raising and lowering the electrodes. If the electrodes are not adjusted in time, a mass of gas can accumulate in the electric arc furnace, which can result in voids in the products. If the backlog gas is excessive, the molten material in the furnace may spray. Moreover, the electrodes position appears excursion during adjustment, and distribution of the materials in the electric arc furnace is not homogeneous, so the temperature around electrodes is high, however the temperature around other electrodes is low. The imbalance distribution of heat would influence the quality of products. More serious, if the imbalance distribution of heat exists for a long time, in the higher temperature portion of the electric arc furnace, the temperature rises sharply. And the furnace could be even worn out without effective detection and prevention.
Fault detection and diagnosis have been the key means to ensure the safety of equipment and personnel and the quality of products. In the past several decades, Principal Component Analysis (PCA) and Partial Least Square (PLS) have been used widely in industrial production and got lots of satisfying results. Multivariate Statistics Process Control (MSPC) has also been studied deeply. However, there is often more than one operating mode in the electric arc furnace, so fault detection of the multiple modes of production and multimode productive process becomes more complicated. There is often a lot of problems in the multivariate statistical process control (MSPC) applied to the multimode production process. MSPM may sometimes make some mistakes, even if the production process is working in another steady-state operation mode. The recursive PCA and self-adaptive PLS arise over these years. Although these methods can also be used for online fault detection, it still lacks the ability to deal with the multimode operating process, and the detection results are unsatisfactory.
Moreover, because when the arc forms the energy is concentrated and the temperature of the arc zone near the electrodes could be above 3000° C., it is hard to measure. Temperature can be got by observing the temperature of the furnace wall in the traditional production process. The temperature of the furnace wall and that of the molten materials inside the electric arc furnace are usually different because there are specific heat capacity and thermal resistivity. But the temperature in the electric arc furnace is hard to measure. The traditional thermocouple measures temperature by contact, but the thermocouple will melt at high temperature. Therefore, the costs of temperature measurement increase greatly with the raising of the temperature. In this case, some engineers and technicians try to invent advanced thermocouples which can be used at higher temperature by changing the materials. Although the range of temperature which can be measured is widen, due to the restriction of the contact temperature measurement technology, the equipment is worn out seriously. Therefore, the durability of the equipment is affected, and more impurities are generated because the materials are molten in the electric arc furnace, which affects the quality of the products.